1. Field of the Invention
The present invention relates to an electromechanical and electroacoustic transducer used for a portable terminal to cause the portable terminal to vibrate upon signal reception and to reproduce an acoustic signal.
2. Description of the Related Art
One example of an electromechanical and electroacoustic transducer used for a portable terminal (e.g., cellular phone) is disclosed in Japanese Patent No. 2,963,917. This electromechanical and electroacoustic transducer includes a single vibration system that is actuated with a low frequency signal (i.e., call arrival notification signal) or an audio signal. The call arrival notification signal causes the vibration system to vibrate when the portable terminal receives a call, in order to notify a user of the portable terminal of an incoming call. The audio signal also causes the vibration system to vibrate so as to produce a sound (or to reproduce an acoustic signal). The vibration system therefore has to possess vibration response characteristics which are suitable for both mechanical vibrations and acoustic vibrations. In order to drive the electromechanical and electroacoustic transducer, a vibration circuit is required to produce vibrations upon receiving a call, and a switchover circuit is also required to select one of the audio signal and the incoming call notification signal so as to transmit the selected signal to the electromechanical and electroacoustic transducer.
An object of the present invention is to provide an electromechanical and electroacoustic transducer having a vibration system which only requires a relatively simple vibration response characteristic and which does not require a complicated drive circuit.
According to one aspect of the present invention, there is provided an electromechanical and electroacoustic transducer comprising a permanent magnet, a yoke member for forming a magnetic circuit together with the permanent magnet, a magnetic gap being formed in the magnetic circuit, a voice coil placed in the magnetic gap, an oscillation plate coupled to the voice coil, a vibration coil adjacent to the permanent magnet, a resilient member for supporting the vibration coil such that the vibration coil can move relative to the yoke member or the yoke member can move relative to the vibration coil, and a switching element connected in series to the vibration coil and turned on and off upon movements of the yoke member relative to the vibration coil. The yoke member moves when the vibration coil is energized. The electromechanical and electroacoustic transducer only includes the single permanent magnet and has a compact structure. The two independent vibration systems share the single permanent magnet. One vibration system is utilized to reproduce an acoustic signal and the other vibration system is utilized to produce physically sensible vibrations. The electromechanical and electroacoustic transducer can be therefore actuated with a simple circuitry.